In plasma-based systems, one or more radio frequency (RF) generators generate RF signals. The RF signals are provided to a plasma chamber to generate plasma within the plasma chamber. The plasma is used for a variety of purposes, e.g., to etch a wafer, to clean a wafer, to deposit materials on a wafer, etc.
As time has progressed, a wafer and any layers deposited on the wafer have become thin. When a layer is thin and etching is performed, various techniques, e.g., an interferometric endpoint detection technique, a time measuring technique, etc., are used to determine whether the etching is to be stopped.
However, regardless of whether the techniques are used, the etching may occur in undesirable areas on the wafer or on a layer on top of the wafer.
It is in this context that embodiments described in the present disclosure arise.